Lots of wild soybean strains (Glycine soja) collected from various parts of Japan were grown in pots at the farm of Faculty of Agriculture, Iwate University, in 1970. The harvested seeds were an-alyzed for protein percentage by macro-kjeldahl method (6.25×N) and sulfur-containing amino acid contents (methionine, cystine, and total, respecti-vely) by micro-biological assay. Potenciality as gene sources for protein improvement of cultivated soybean was discussed. Thereafter in 1972, a part of the strains stated before and the other strains, newly collected from Tohoku district (northern part of Honshu island, Japan), mainly lwate-ken, were grown in pots with similar purpose. Only seed protein percentage was determined.